In the context of long-term archival of digital assets, file formats that are standardized and designed for longevity such as PDF/A are preferred. However, due to the complexity and ambiguities in PDF standards, it is far from trivial to either create standard-conformant files or check the conformance of any given file. This study aims at investigating the challenges when checking real-world PDF files from public sector organizations meant for long-term archival for PDF/A conformance. Results show that only a small set of PDF files claims to conform to the PDF/A-1b specification variant and even fewer files pass conformance checks by various conformance checking tools. Challenges for conformance checking tools include both ambiguities in the standards’ technical specifications and limitations in the implementation.